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Vertex, Ligand, TG Therapeutics, and Isis are the top biotech stocks to watch this Tuesday morning.

Let's take a look at four stocks which could loom large in biotech headlines this morning -- Vertex Pharmaceuticals (NASDAQ:VRTX), Ligand Pharmaceuticals (NASDAQ:LGND), TG Therapeutics (NASDAQ:TGTX), and Isis Pharmaceuticals (NASDAQ:IONS).

Vertex soars over 50% on positive cystic fibrosis treatment dataVertex Pharmaceuticals is up more than 50% in pre-market trading this morning, after it announced that an experimental cystic fibrosis (CF) combination regimen had met the primary endpoints in two phase 3 trials compared to a placebo. CF is a rare genetic disease which causes the buildup of thick mucus that can damage the lungs.

Vertex's CF treatment is a combination of two drugs -- VX-809 (lumacafator) and Kalydeco (ivacaftor). Pooled analysis of the two phase 3 studies showed that the combination regimen showed statistically significant reductions of 30% and 39% in the rate of pulmonary exacerbations when compared to the placebo. Vertex plans to submit marketing applications in the U.S. and Europe based on these positive results.

If approved, Vertex's combination will be the first treatment for the underlying disease of CF in patients with two copies of the F508del mutation, the most common form of the disease. Analysts believe the combination regimen could generate peak sales between $4 billion to $6 billion.

Vertex currently has two marketed products -- Kalydeco for CF and Incivek for hepatitis C. In 2013, Vertex reported $466.3 million in revenues from Incivek (which is marketed by Johnson & Johnson overseas as Incivo) and $371.3 million in revenues from Kalydeco. The remainder of Vertex's top line mainly comes from royalties and collaborative payments.

Ligand announces a new partnership with TG TherapeuticsMeanwhile, Ligand Pharmaceuticals and TG Therapeutics just inked a new partnership to develop and commercialize Ligand's IRAK-4 (Interleukin-1 Receptor Associated Kinase-4) inhibitors in a preclinical program for treating certain cancers and autoimmune diseases. IRAK-4 is a protein kinase which plays a key role in immunity and inflammation. Ligand originally acquired the IRAK-4 inhibitors from its acquisition of Pharmacopeia in 2008.

Ligand will receive 125,000 shares of TG common stock worth approximately $1 million, and is eligible to receive $207 million in potential milestone payments. If the IRAK-4 products are approved, Ligand will earn tiered royalties between 6% to 9.5% on net sales.

Investors should also note that Ligand's partner GlaxoSmithKline(NYSE:GSK) recently announced positive data from its phase 3 trial of Promacta/Revolade in pediatric patients with chronic immune thrombocytopenia. The drug achieved its primary endpoint and achieved a statistically significant improvement in platelet count in 39.7% of patients compared to 3.4% for the placebo. Promacta is expected to generate peak sales of $300 million if approved, which translates to $15 million to $20 million in royalties for Ligand.

Both developments are positive for Ligand, which only reported $49 million in revenues in 2013. However, shares of Ligand remain unchanged this morning in pre-market trading.

Isis receives a milestone payment from GlaxoSmithKlineLast but not least, Isis Pharmaceuticals just earned a $1 million milestone payment from GSK related to the advancement of its phase 2/3 study of ISIS-TTRRx in patients with familial amyloid polyneuropathy.

ISIS-TTRRx is an experimental drug for the treatment of transthyretin amyloidosis, a rare genetic disease which causes the dysfunction of peripheral nerve and heart tissues. Including the current payment, Isis has earned $26 million (out of $50 million in potential payments) in upfront and milestone payments related to the advancement of ISIS-TTRRx. GSK can also exercise its option to exclusively license the entire program, which will grant Isis license fees, regulatory and milestone payments, and double-digit royalties on sales of ISIS-TTRRx.

Although GSK's latest milestone payment is small, it's a positive sign for the development of ISIS-TTRRx and the rest of Isis' pipeline. Isis also recently reported new milestone payments from AstraZeneca and Biogen recently. Shares of Isis are up 2% in pre-market trading this morning.

Leo Sun has no position in any stocks mentioned. The Motley Fool recommends Isis Pharmaceuticals, Johnson & Johnson, and Vertex Pharmaceuticals. The Motley Fool owns shares of Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.

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Leo is a Tech and Consumer Goods Specialist who has covered the crossroads of Wall Street and Silicon Valley since 2012. His wheelhouse includes cloud, IoT, analytics, telecom, and gaming related businesses. Follow him on Twitter for more updates!